Halfway through my pregnancy, and I’m relieved to say that I am finally starting to look pregnant – rather than just fat. My waistline appears to have grown 2 inches in a week, and my expanding belly is a fertile topic of conversation among friends and strangers.

After “When is it due?” and “Do you know its sex yet?” the question I get asked most is “Have you had any strange food cravings?” Even my dad is getting in on the act&colon; the first thing he asked me upon learning I was pregnant was “Have you been licking any coal?”

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Apparently, some pregnant women develop a taste for minerals or even metallic objects during pregnancy, a phenomenon known as “pica“. This could be a result of anaemia.

Junk-food yearnings

I haven’t been craving coal, but I have developed a taste for cakes and junk food. I also, rather weirdly, went off salad for about six weeks during the first trimester, when I usually love the stuff. Pregnant friends affirm similar cravings for junk food and a voracious appetite.

So has anyone come up with a persuasive explanation for these cravings? A review paper in the latest issue of Chemosensory Perceptionexplores the issue in detail. Surprisingly, very little research has been done on the dietary quirks of pregnant women, but studies on rats and insights from the hormonal changes that take place during women’s menstrual cycles are providing some clues.

Such studies consistently find that pregnant women develop an increased desire for salty foods, combined with a diminished sensitivity to their taste. This may be because pregnant women require slightly more salt to maintain osmotic pressure (or fluid balance) as their blood volume expands. Rats eat more salt during pregnancy, too.

Pregnant women are also more sensitive to bitter foods. “This may be an adaptation in order to avoid intake of bitter-tasting, toxic compounds,” says Marijke Faas of the University Medical Centre in Groningen, the Netherlands, and lead author of the Chemosensory Perception paper. She tells me my aversion to salad leaves may reflect increased sensitivity to bitterness – although she has never heard of other women shunning lettuce.

Eating for two?

As for my insatiable appetite, increased levels of progesterone may be to blame. Both human and animal studies have shown that this hormone increases appetite and oestrogen decreases it. “Although both hormones are increased during pregnancy, there is relatively more progesterone than oestrogen during pregnancy,” Faas says.

This may be why I overindulged at Easter, and am now a couple of kilograms over the recommended target for weight gain at this stage of pregnancy. My friends assure me that I should be eating for two, but my fetus currently weighs only about 280 grams, which pretty much knocks that idea on the head.

In fact, nutritionists recommend upping food intake by only about 300 calories a day during the last two trimesters, and excessive weight gain by women during pregnancy is linked to obesity in their kids.

So perhaps it’s a good job that I’m able to face the lettuce leaves once more. Salad for dinner anyone?